In highly automated electric vehicles, the reliability of electrical powertrain system is much more important, because there may be no driver available. In case of a critical failure in the electrical machine, the vehicle may breakdown on an active traffic lane and the safety of passengers cannot be ensured. To avoid these dangerous situations, these failures should be detected at an early stage. This paper focuses on a common failure, interturn short-circuit failure, in a stator winding of an interior permanent magnet synchronous machine (IPMSM). A mathematical model of IPMSM in normal and failure case is presented. Then, four failure-sensitive machine properties are chosen as detection indicators. A sensitivity analysis is given to illustrate their dependencies on fault severities and operating points. According to the result, the best operating point for the detection is found and a test route is designed to validate the effectiveness of this concept.